Before starting this project, check your local and state laws regarding the rules for collecting rainwater.

Material Availability

Readily available

Cost

High ($100 - $150)

Safety

Wear safety goggles and equipment when working with tools. Minor injury is possible. Adult supervision is required. Do not drink the water collected in the project.

*Note: This is an abbreviated Project Idea, without notes to start your background research, a specific list of materials, or a procedure for how to do the experiment. You can identify abbreviated Project Ideas by the asterisk at the end of the title. If you want a Project Idea with full instructions, please pick one without an asterisk.

Abstract

We are all familiar with the nursery rhyme, "Rain, rain, go away, come again some other day...", or
the song "Singin' in the Rain." Numerous songs and stories describe our feelings about rain. Why so many?
Because we humans understand how important rain is to our well-being. Rainfall, as part of the
water cycle, brings water back to Earth that had previously evaporated or transpired
from the surface. When water vapor in the atmosphere condenses into clouds and falls back to Earth as rain,
it lands on oceans, lakes, and the ground, where it soaks in and recharges the groundwater supply.
Groundwater serves humans, animals, plants, and microorganisms alike.

For the people who live in the Thar Desert of India and in the western part of the semi-arid Sahel and
Sudan belt that crosses Africa, the rain that falls during the monsoon season is especially important
because it is often the only source of water. The monsoon occurs in certain parts of the world when seasonal
winds reverse, bringing in dramatic weather changes. Summer monsoons usher in heavy rains while winter
monsoons can result in drought. In these parts of the world, collecting rainwater is an important
task, one that provides both drinking and cooking water. For hundreds of years, the people living here
have developed different methods of collecting water. Watch this video of a talk given by Anupam Mishra, a
founding member of the Gandhi Peace Foundation. He travels across India studying and sharing rainwater
harvesting techniques.

Watch this video in which Anupam Mishra gives a TED talk on rainwater collection
techniques practiced by Indian desert dwellers. (Video by TED.com)"

You may think that collecting rainwater is an ancient art practiced only by people living in arid and
developing regions of the world, but this is not true. People in urban areas collect rainwater, too,
although it is a non-potable water source. This means that it is not safe to drink. However, it
can still be used to water landscaping and to flush toilets. While this rainwater may contain
contaminants, such as chemicals, molds, dirt, bird feces, and leaves, consumers can take measures to
clean and disinfect the water, with ozone or chlorine, and then they can drink it. Using rainwater is a way
to reduce dependence on the municipal water utility, alleviate runoff, and live a sustainable,
"green" life.

One common way of collecting rainwater is to divert the rainwater from a rooftop. Simply, the rain flows
down the roof, into a gutter, and then into a holding tank. Holding tanks can be made from clay, cement,
wood, or plastic. Figure 1 shows a concrete rainwater tank in Kerala, India. Notice the gray pipe that
connects the tank to the roof.

Figure 1. A 35,000-liter rainwater harvesting tank in the state of Kerala, India. (Wikipedia, 2011)

The tank is covered to prevent mosquitoes from breeding in it, and to keep leaf litter and other large
foreign objects from falling in. Toward the bottom and on the side of the tank is a spigot, to which a
hose can be connected. Some complicated systems have first-flush valves (to discard the water from the
first rainfall, which likely has roof debris and particles in it), filters that remove particulates and
harmful substances, and disinfection systems that kill bacteria. Disinfection occurs as the last step,
just before ingestion of the water.

For your science project, try designing and building a rainwater collection system for non-potable
water use. Remember that the collected water is not for drinking. The Engineering Design Process guide can help you organize your thoughts on how to get started. In addition, there are several sources online from which
you can get ideas and plans on how to build a collection system. The references in the bibliography are a
good starting place, but make sure to do your own research. You will have to take several issues into
account, the most important being that the collection of rainfall in some states in the United States is
subject to water-rights limitations. Look into your state's water laws prior to starting this project.
Another issue to consider is the kind of roof you will be collecting the water from. What kinds of roofs
add contamination to the water? Is one type of roof better for collecting rainwater than another? What is
the average rainfall in the area in which you live? How much water can you harvest in a month? In six months?
How much money can your household save? Is collecting rainwater useful for your household?

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